What was the name of McDonald's first nationally promoted breakfast sandwich?

The Egg McMuffin was McDonald's first nationally promoted breakfast sandwich.

Herb Peterson created the sandwich in 1971 at his McDonald's restaurant in Santa Barbara, California. It combined a toasted English muffin, egg, Canadian bacon, and cheese in a compact format that could be prepared and eaten conveniently in the morning.

The sandwich helped give McDonald's breakfast branding a signature product. McDonald's had offered breakfast items before, but the Egg McMuffin provided a distinctive menu identity that could be promoted nationally. Its name also extended the chain's “Mc” naming pattern into a new daypart.

The Egg McMuffin is sometimes confused with later breakfast products such as the McGriddle. The McGriddle was introduced decades later and uses sweet griddle cakes, while the Egg McMuffin established the classic English-muffin format.